The present invention relates to fittings for hose ends and more particularly to end fittings for hoses that are constructed to transport reactive fluids through ambient reactive fluids where either fluid, or both, may react with and destroy seals in the hose fittings.
It is often necessary to transport reactive fluent media through a gaseous or liquid medium that is also reactive. Sometimes the pressure differential between the media is substantial. Constructing hose end fittings where the juncture of the tube and fitting does not leak when subjected to high internal hose pressure has been a perennial problem. In the case of metal hoses, various different approaches have been taken. Some fittings have been hermetically welded or brazed onto the metal tubes. Where chemically reactive media are transported the materials used for the tube and fitting were special alloys that were difficult to weld or braze. Constructing these kinds of fittings required specialized equipment and skilled operators.
When hoses have been constructed from annularly corrugated tubes, fittings formed from members that are screwed together to crush interposed tube corrugations were sometimes employed. Usually the corrugations were crushed against a sealing face formed on one fitting member. Caulking material was sometimes applied where the crushed corrugations were seated to block leakage paths. In other hoses, rigid washer-like seating rings were associated with the sealing faces so that the corrugations were crushed against the seating ring.
Although these last mentioned fitting constructions were relatively easily assembled to corrugated tubes without requiring sophisticated tools or machinery, the hose performance was not optimal because leakage occurred after repeated usage. Hose flexures and repeated internal hose pressure cycling caused leakage paths to develop. Furthermore, in applications where the hoses directed reactive fluids through reactive atmospheres or liquids, sealant materials in the fittings were subject to being attacked by either reactive fluid, leading to leakage and fitting failures.
The present invention provides a new and improved metal hose and method of making the hose wherein the tube and end fitting are assembled without the need of specialized equipment or skilled labor, and the juncture of the end fitting and hose is resiliently sealed against leakage into or from within the hose by first and second seals that seal the hose while individually preventing the other seal from contacting potentially damaging reactive materials.
The present invention provides a hose end fitting that comprises an annularly corrugated imperforate metal tube, a fitting member fixed to an end of the tube, and, first and second resiliently compressible sealing members. The metal tube has axially spaced apart outer corrugation peaks and axially spaced apart inner valleys, each valley interposed between two of the peaks. Adjacent peaks and valleys are connected together by generally inwardly extending tube walls so that the tube defines an axially extending tube flow path through which fluent material may pass. The fitting member comprises a fitting body defining a through opening, a seal seat surrounding and extending outwardly from the through opening, and a tube compressing extension projecting from the fitting body. The tube compressing extension defines a tube corrugation positioner surface distal the fitting body and seal seat, and a tubular wall extending between the positioner surface and the fitting body. The first sealing member is shaped to sealingly engage the seal seat and is resiliently engaged with and between the seal seat and the tube end to prevent leakage of fluid from within the hose beyond the first sealing member. The second sealing member is spaced axially from the first sealing member and disposed between the first sealing member and the tube corrugation positioner surface. The second sealing member is resiliently compressed between adjacent inwardly extending tube walls and sealingly engages at least one of the adjacent tube walls and the tubular wall of the tube compressing extension. The second sealing member thus blocks fluid leakage from outside the hose into the space between the sealing members. The first and second sealing members are constructed from dissimilar materials.
In the illustrated embodiment the new fitting is fabricated by constructing a metal tube having a corrugated wall with successive corrugations defining inner and outer peaks joined by imperforate tube wall sections, terminating the tube adjacent a corrugation peak and fabricating a tube end fitting that comprises forming a fitting body having a through opening and a seal seat that surrounds the through opening with the seal seat extending outwardly relative to the through opening, and forming a tubular extension that projects from the fitting body and defines a tube corrugation positioner surface distal the fitting body. A first resiliently compressible sealing member is assembled to the fitting body in contact with the seal seat. A second resiliently compressible sealing member is assembled to the tube by placing the sealing ring between adjacent outer peaks that are located in the vicinity of the tube terminus. The fitting body is placed on the terminated tube end with the tube terminus engaging the first sealing member and the tube corrugation positioner located at least one outer corrugation peak from the second seal member. The extension is deformed to move the corrugation positioner surface into engagement with the tube just beyond the outer corrugation peak and axially compress the tube corrugations between the positioner surface and the seal seat. The second sealing member is resiliently compressed between the adjacent outer peaks and urged into sealing engagement with the tubular extension while the first sealing member is compressed between the tube terminus and the seal seat